Aspergillus niger strains MTCC 281 and KLP20 immobilized on polyurethane foam were utilized for the batch fermentation of citric acid from carob pod extract. Carob pods are the fruits of carob tree (Ceratonia siliqua). Carob pod extract with 40-50% sugars were inoculated with immobilized polyurethane foam and incubated at 30 °C. Maximum citric acid yields of 23 and 33 g L-1 with free and immobilized cells in case of A. niger MTCC 281 and 27 and 38 g L-1 in case of A. niger KLP20 were obtained after 72 h of fermentation. From the studies A. niger KLP20 seems to be a potential strain among the two strains for the maximum citric acid production.
